1. Field of the Invention
This invention relates to a system for remotely controlling the open/close status of individually selected circuit breakers in a panel of such circuit breakers which provide overload current protection.
2. Description of the Prior Art
Circuit breakers provide overcurrent protection for preventing personal injury and property damage. A loadcenter or panelboard receives electrical power from the utility company transformer and routes the electrical power through a main circuit breaker and then through branch circuit breakers to designated branch circuits, each supplying current to one or more electrical loads. The circuit breakers are designed to interrupt the electrical current if it is excessive or outside the design limits of the conductor and loads, to reduce the risk of injury and damage. Branch circuit breakers are provided in narrow width molded cases which fit into designated slots or pole openings in the panelboard.
A circuit breaker has a thermal/magnetic trip characteristic. The thermal characteristic is operative in response to overload current of extended duration which heats a bimetal member, causing movement of the latter, which in turn releases a latch to trip open a set of contacts. For example, the thermal characteristic would respond to 30 amps being drawn in a 15 amp circuit. The magnetic characteristic is operative in response to a sudden high magnitude current overload condition, and uses the magnetic field generated in a magnetic core to attract an armature, which movement releases the latch to open the contacts. As an example, the magnetic type actuation occurs in response to a short circuit wherein the hot line conductor becomes directly connected with ground or neutral, bypassing the load.
It is known in the prior art to provide remote controlled circuit breakers wherein the breaker contacts are tripped to an open condition by an actuator responding to a control signal. This enables the circuit breaker to additionally perform a switching function and manage a load connected to the breaker, such that the breaker performs the dual functions of overload current protection and load management. Such systems are disclosed for example in U.S. Pat. No. 6,034,581 for controlling lighting systems based upon the time of day and ambient light; and in U.S. Pat. No. 5,373,411 which utilizes a circuit breaker panel to control household appliances.
However, a disadvantage of using the breaker contacts to perform such switching relay type function is that the breaker contacts are designed to interrupt high current, not for repeated operation. Also, such prior systems for remotely operating a panel of circuit breakers requires wired connection between the panel and sensors which deliver a monitoring signal to the panel. Such wiring is generally impractical unless installed into a building at the time of its construction. Even so, it is a costly installation.
U.S. Pat. No. 5,477,016 to Baginski et. al. discloses a control unit having mechanical features adapted to move the circuit breaker between open and closed states. However, the add-on unit is intended as a permanent installation which permits locking of the circuit breakers in their open position.
When an electrician is working on features of the electrical system of a residential or commercial building, he often finds it necessary to turn the electrical service on and off at the appropriate circuit breaker. Considerable time is wasted in going back and forth to verify or change the status of circuit breakers.
It is accordingly an object of the present invention to provide a system for remotely controlling circuit breakers in an electrical panel having a number of said circuit breakers.
It is another object of this invention to provide a remote control system as in the foregoing object having mechanical components which are removably installable upon said panel.
It is a further object of the present invention to provide a remote control system of the aforesaid nature which additionally provides remote verification of the status of said circuit breakers.
It is still another object of this invention to provide a remote control system of the aforesaid nature which is inexpensive and easy to use.
These objects and other objects and advantages of the invention will be apparent from the following description.